This invention relates to material handling devices. More specifically, this invention is a grapple that can be used with robotic or other material handling devices for manipulating, i.e. contacting, grabbing, holding and releasing objects, particularly those having undefined shapes such as sacks and bags.
A large number of grapples have been invented for various robotic devices to maneuver solid objects such as boxes and industrial components in manufacturing and production settings. Although quite useful for various industries, these grapples are not able to grab and hold sacks and bags effectively. Postal services across the world use sacks to hold letters, magazines and small boxes. These sacks are handled manually by mail handlers. Most sacks used by US Postal Service (USPS) do not have eyelets, handles or any form of operator interface for grabbing. The shape, size, and the weight of a sack depend on the items in the sack and how the sack is rested on the floor. Sacks fully filled with magazine bundles may weigh up to seventy pounds. The heavy weight of these sacks, the lack of handles, eyelets, or any kind of operator interface on the sacks, and the unpredictable shape and size of the sacks have created awkward and uncomfortable handling situations for U.S. mail handlers particularly at USPS distribution centers. During repeated maneuvers, the awkward sack handling increases the risk of wrist, finger and/or back injuries among mail handlers.
U.S. Pat. No. 4,181,345 (Achelpohl) describes a manually operated clamping device for lifting filled sacks. The device includes a frame supporting a clamping mechanism. The clamping mechanism includes two spaced parallel bars, mounted at their end to two parallel plates and disposed to be rotated in unison about a common parallel axis by a hand-crank. One of the bars is individually rotatable about its own axis and displaceable towards and away from the other bar. To use this device, the gathered top of a filled sack must be manually placed between the two bars. The hand crank is manually operated to wrap the top of the sack around the two bars and clamp it between them. Once secured in the clamping mechanism, the combined clamping device and sack may then be lifted by the device""s frame. Unfortunately, this device requires considerable manual manipulation of both the sack and the device.
In an attempt to overcome some of the disadvantages of the device taught in the ""345 patent, Achelphol developed a similar device, U.S. Pat. No. 4,226,458 (Achelpohl), in which the clamping bars are mechanically separable and are mounted only at one end to a frame, such that they form parallel cantilever arms. This allows the gathered ends of a sack to be inserted between the clamping bars. The end of the sack is then engaged by mechanically operating the clamping mechanism. Although this device improves the manual operation required by the ""345, the device taught in the ""458 patent still requires either the gathered end of a sack to be manually placed between the clamping bars, or the sack to be placed on its bottom and the top of the sack gathered, flattened and presented in a proper configuration, so that the device can slideably engage the top of the sack and secure it for lifting.
U.S. Pat. No. 4,549,760 (Minenko et al.) discloses a device for gripping and hoisting packed sacks that utilizes a similar mechanism similar to that of the ""458 patent for grabbing, and it has many of the same disadvantages. However, in the device taught in the ""760 patent, one of the bars moves relative to the other, with the help of a hydraulic linear actuator. The ""760 device still requires the gathered end of a sack to be manually placed between the clamping bars. In this case, the sack is placed on its bottom next to the unpowered bar. The second bar, powered by an actuator, moves around the first bar causing the throat of the sack to be secured in between the bars.
U.S. Pat. No. 4,852,927 (Minenko et al.) describes using two clamping bars to grip and hold the neck of a sack for lifting and transport. The ""927 device includes a locking mechanism to secure the clamping bars in a closed position while gripping a sack. However, the ""927 device requires that the neck of the sack be manually inserted between the clamping bars, then the device must be manually operated to close and lock the neck of the sack within the device. As a result, the sack cannot be released from the device without first removing the load from the locking mechanism.
All of the devices described in the above patents have the following common characteristics and disadvantages. An operator, prior to grasping, must carefully place the gathered and flattened edge of the sack between two adjacent bars. One of the bars rotates around the other one or both bars rotate along a common parallel axis. The gathered and flattened edge of the sack then raps around the bars. The weight of the sack itself pushes the rods against each other and locks the edge of the sack in between the bars. Additionally, the sack must be placed on its bottom. Since a great deal of operator intervention is required for proper and safe operation, lifting operations using the devices described above are slow. Accordingly, these devices have not been employed by the USPS, and many other distribution centers, where sacks need to be rapidly and repeatedly lifted from a shoot or from a conveyor belt.
Therefore, a need remains in the art, which is met by the present invention, for a device that reduces the amount of manual operator intervention required so that the risk of injuries to workers is minimized and operational efficiency is increased.
The present invention provides an embodiment of a grapple device and a method for manipulating objects. The embodiment of the grapple of the present invention is mounted to a transport mechanism and provides, for example, a device that can grab a deformable object, such as sacks and bags, wherein (i) the sack does not need to be oriented, (ii) the edges of the sack do not need to be gathered and flattened for grabbing, (iii) no operator intervention is required for grabbing, and (iv) the weight of the sack is not used to lock and secure the sack in the grapple device. The present invention minimizes risk of injuries to workers and increases operational efficiencies.
A preferred embodiment of the present invention provides a grapple device for manipulating, i.e., contacting, grabbing, holding and releasing, objects, wherein the grapple device further comprises (i) a supporting bracket assembly mountable to the transport mechanism; (ii) a first roller, having a roller axis, the roller rotatably mounted on the supporting bracket assembly, and the first roller being rotatable about its axis, wherein the first roller further comprises a gripping surface for engaging and dragging the graspable portion of the object; (iii) a second roller, having a roller axis, and the second roller being rotatable about its axis, wherein the second roller further comprises a gripping surface for engaging and dragging the graspable portion of the object; (iv) a left pivoting bracket assembly and a right pivoting bracket assembly connected to the supporting bracket assembly, having an axis of rotation and rotatably holding the second roller; (v) a biasing means to bias the rollers toward each other with sufficient force to facilitate holding the graspable portion of the object in place between the rollers; (vi) a first gear, rotatably rigidly connected to the axes of the first roller; (vii) a second gear, rotatably rigidly connected to the axes of the second roller; (viii) a third gear, rotatably mounted on the supporting bracket assembly, wherein the third gear mates with the first gear; (ix) a fourth gear, rotatably mounted on the supporting bracket assembly, wherein the fourth gear mates with both the second and third gears and has the same axis of rotation as the left and right pivoting bracket assemblies; and (x) a drive means for rotating the third gear.
As provided in this preferred embodiment, the supporting bracket assembly is mounted to the transport mechanism by a mounting bracket.
The grapple of the present invention further provides that the left and right pivoting bracket assemblies comprise a first clamping bracket and a second clamping bracket, wherein the first clamping bracket comprises a first end rotatably connected to the supporting bracket assembly and a second end pivotally attached to the first end of the second clamping bracket, and wherein the second end of the second holding bracket rotatably holds the second roller.
Additionally, in the preferred embodiment of the grapple of the present invention, when the drive means rotates the third gear in a first direction, the first roller and the second roller rotate in opposite directions, and when the roller surface of the first roller is placed into contact with the graspable portion of the object, the first roller surface draws the graspable portion of the object into a region between the first and the second rollers, thereby grasping the object. The drive means in the preferred embodiment is a motor and a power transmission system to transmit power from the motor to rotate the third gear. Moreover, in this embodiment, the power transmission system comprises a speed reducer transmission coupled to the motor, a drive sprocket connected to the speed reducer transmission, a driven sprocket connected to rotate the third gear and a chain connecting the driver and driven sprockets.
Furthermore, the preferred embodiment the grapple of the present invention also provides a holding means, preferably a brake, selectively operable to releasably engage at least one of the rollers, and prevent rotation of the roller when engaged, so that when the graspable portion of the object is located in the region between the rollers and the holding means is engaged, the contact between the graspable portion of the object and the first and second rollers causes the object to be held by the device.
Finally, a preferred embodiment the grapple of the present invention also provides when the drive means rotates the third gear in a second direction, the first roller and the second roller turn outwardly, releasing the object.
In addition, the biasing means to bias the rollers toward each other in the preferred embodiment is a spring. Also, in the preferred embodiment of the present invention, the gripping surface of the rollers is covered with a material with a high coefficient of friction, preferably rubber.
The preferred embodiment of the present invention also provides a control system, which following contact with a deformable object, controls the three operational phases of the grapple: grab, hold and release. The control system comprises a signal generating element, preferably a proximity switch, that generates a signal when the grapple is close to an object. The control system further comprises a signal generating element, preferably an electromechanical switch, that generates a signal when a sufficient portion of the object is collected between the rollers. Finally, the control system further comprises a signal generating element, preferably a momentary switch pressed by an operator, that generates a signal to release the object.
The present invention also provides a method of manipulating an object comprising (i) mounting the grapple device described above to a transport mechanism, (ii) positioning the grapple device close to the object, (iii) activating the grabbing operation of the grapple device, (iv) stopping the rotation of the rollers automatically when a sufficient portion of the object is grabbed between the rollers, thereby holding the object, (v) maneuvering the grapple device and object, via the transport mechanism, to the desired location, and (vi) releasing the object from the grapple device. The method further comprises releasably engaging at least one of the rollers to prevent rotation of the roller when engaged, so that when the graspable portion of the object is located between the rollers, the contact between the graspable portion of the object and the first and second rollers causes the object to be held by the grapple. Additionally, the method of manipulating an object of the present invention further comprises, (i) generating a signal when the grapple is close to an object, (ii) generating a signal when a sufficient portion of the object is collected between the rollers, and (iii) generating a signal to release the object.